In the past 15 years, women’s tennis has been nothing if not orderly. From Steffi Graf and Monica Seles on through Martina Hingis, Serena Williams, and Justine Henin-Hardenne, there’s always been a frontrunner, someone whose defeats were cause for surprise, if not alarm.

The only woman other than those five to finish a year atop the rankings is, of course, Lindsay Davenport, who did it in 1998, 2001, and 2004. But Davenport was something of a lame-duck no. 1 during her first two stints,and after her loss to Serena Williams Saturday at the Australian Open – in which she was flummoxed for 10 consecutive points at the most critical moment – it’s clear that she won’t rule for long.

Unlike years past, though, there’s no clear successor in the offing. One of four or five women could take charge of the tour this year, or none at all. If injured Belgians Henin-Hardenne and Kim Clijsters recover their abilities, it’s anyone’s guess as to who might win out. Even Hingis, who is playing her first tournament in two years this week in Thailand, wants in on the action.

In terms of talent, Serena has the most to offer, and she certainly proved these last two weeks that she has the intensity and grit of a champion. Still, one could hardly expect her title run to inspire fear in her colleagues. Visibly not in top shape and still timid at times on her forehand, she was nearly beaten twice in three days, surviving by virtue of Maria Sharapova’s failure to convert three match points and Davenport’s implosion. Even if she recaptures her top ranking – and it’s a safe bet that she will, at least for a time – the aura is gone. Reality is even harsher for her sister Venus, who is no longer a contender for the top ranking.

Can Sharapova take the top spot? At 17, she has impeccable strokes, a smooth serve, and a competitive drive that rivals Serena’s. She is the next obvious choice, but she’ll have to work on her movement and develop more tactical variety, both skills that can be improved with practice. It would be sur prising to see Sharapova at the top by the French Open, the Grand Slam she’ll likely have the most trouble winning.

As much as has been made of the Russian contingent, only Sharapova and Svetlana Kuznetsova have the talent to sustain a no. 1 ranking. Anastasia Myskina doesn’t hit with enough force, Elena Dementieva has the most flawed serve on the tour, and Nadia Petrova becomes flustered in tense moments.

Kuznetsova may yet prove to be the best of the Russians. Her legs are incredibly strong, giving her great court coverage and balance. She’s no weakling when it comes time to serve, either; when she’s in a groove, Kuznetsova is liable to wipe the court with almost anyone. Unfortunately, she’s still likely to make troubling errors in bunches.

Then there are the Belgians. Clijsters hasn’t played in a year, though she says she plans to return soon. Her tennis is consistent and she covers the court as well as anyone. Like Amelie Mauresmo, she tends to crumble under pressure, but with one big win,she just might find her way.

Henin-Hardenne seemed destined to lead the pack for the next few years before she was felled by a virus and, more recently, a knee injury. She won three out of four Grand Slams from the summer of 2003 through last year’s Australian Open, and even after a long layoff, she flew to Athens and came home with an Olympic gold medal.

Henin-Hardenne’s variety and grace make her the most enjoyable woman to watch, and one can only hope that she will regain her form. If she does – and her competitors continue to improve – we should all be in for a rare treat: a stretch of parity and rivalries in women’s tennis the likes of which we haven’t seen in years.